Automate manifesto signing: form → mailing list + auto-published signatory list

[rufuspollock]

Currently manifesto signing is a Google Form processed manually (signatories hand-added to manifesto.md).

Desired:

1. On signup, signatory is added to the mailing list (Substack or ESP — pending email-infra decision, see devspaces-consolidation/BRIEF.md).
2. Signatory list on /manifesto updates automatically (with consent + affiliation-disclaimer handling).

Needs its own mini research/plan:

• Options: Google Form + Apps Script → commit to repo / Brevo form + API → build-time fetch / Tally+webhook / custom endpoint.
• Consent language for public listing; moderation step to prevent spam signatures.
• Where the canonical signatory store lives (sheet vs repo data file).

Part of the Developmental Spaces consolidation (see life-itself/devspaces-consolidation planning repo: BRIEF.md, PLAN.md).